Filter



June 25, 1968 v H MLLER 3,389,855

FILTER Grignal Filed May 6, 1963 United States Patent O 3,389,855 FILTERHans Mller, Erlenbach, Zurich, Switzerland Continuation of applicationSer. No. 278,216, May 6, 1963. This application May 23, 1966, Ser. No.552,340 Claims priority, application Switzerland, May 19, 1962,6,198/62; Jan. 31, 1963, 1,176/63 8 Claims. (Cl. 233-2) ABSTRACT OF THEDISCLOSURE A centrifuge for separating solid particles suspended in aliquid from the latter, wherein a centrifuging chamber is providedbetween two plates fixed to the driven shaft of the centrifuge andextending axially spaced from each other transverse to the shaft, and anVaxially movable tubular member surrounding the shaft and forming withthe periphery of one of the plates filter means in form of a narrowannular gap through which the liquid may pass while the solid materialwill be retained by the gap and will accumulate on the inner surface ofthe tubular member to be discharged therefrom by moving the tubularmember in axial direction so as to open the centrifugal chamber inradial direction.

This application is a continuation of Ser. No. 278,216 filed May 6,1963, now abandoned.

Centrifuges for separating liquids from solids operate either asdecanting centrifuges, where separation is effected by gravity, or asscreening centrifuges, where the liquid is pressed by centrifugal forcethrough a screen or fabric on which the solid particles are left behind.

One of the disadvantages of both types of centrifuge is that theseparated particles can be discharged from the centrifuging chamber onlywith diihculty. Either they must be discharged by hand, as in the caseof the pendulum centrifuge, or the solid particles are insufiicientlyfreed from liquid and are deposited in the form of a thick sludge.Continuous discharge, as practised for example with the so-called thrustcentrifuge, destroys and crushes the solid particles and can only beused with coarsegrained substances.

A centrifuge has now been found which is free from these disadvantagesand which may be designed both as a decanting and a screeningcentrifuge. In accordance with the present invention, there is provideda centrifuge for separating solids from liquids and having a rotatableshaft, in which two plates fixed to the shaft -form a cavity that servesto accommodate the liquid and that is closed at the periphery by atubular member, the tubular member being adapted to move in thedirection of the axis of rotation so as to enable the cavity to beoutwardly opened and closed.

The liquid may be separated simply be decantation or else, as described,additionally by screen centrifuging. In the case of decantation theliquid is separated in the cavity through deflection by means f apartition wall screening the outlet apertures. In the case of screencentrifuging it is done through a narrow filtering gap which preferablyparallel the axis of rotation, and the filter gap is cleaned of anyseparated solids when the cavity is opened by displacement of thetubular closure member.

The invention is illustrated in the accompanying drawings in which:

FIG. 1 shows a section through a centrifuge in accordance with thepresent invention; and

FIG. 2 shows a section through a modification of the centrifuge.

The basic principles of the centrifuge construction is shown in FIG. 1.Connected to the rotating shaft 300 are 3,389,855 Patented June 25, 1968ice two disc-like plates 307 and 312 which are spaced a certain distanceapart and thus form an annular cavity 301.

The plates 307 and 312 are preferably parallel, although they could alsobe arranged at a certain angle to one another so that the cavity 301 istrapezoidal. At the periphery of the two plates 307 and 312 is a closureto the outside in the form of a tubular member 310, which can be movedin the direction of the shaft 300. Thus the cavity 301 can be closed andopened by lateral displacement of the member 310. The plate 307 is fixedto the end of the shaft 300, whereas the plate 312 is fixed along itsbottom edge to a hollow hub 303 projecting coaxially with the shaft 300from the plate 307.

Lateral displacement of the closure 310 may be effected mechanically,pneumatically, hydraulically, electrically or magnetically.

If the centrifuge, to which the liquid-solid mixture is fed in directionof the arrow 304 through the hollow hub 303 and passage 306, is used asa decanting centrifuge, then it is equipped with an additional plate312' extending substantially parallel to the plate 312 .and connected tothe outer end of the hollow hub 303. The mixture flows into the movingcentrifuge at 306, the heavy solid particles are deposited in thechamber 301, .and the clear liquid flows out of the chamber 301 througha filtration gap 311 formed between the outer periphery of the plate 312.and the inner surface ofthe member 310.

The liquid fiowing out through the filtration gap, formed between theperiphery of the plate 312 and the inner surface of the axially movabletubular member 310, enters an intermediate chamber 308 formed betweenthe plate 312 and the additional plate 312. The plate 312 is formed at aradially inner portion thereof with at least one decanting passage 305and the additional plate 312' having .a radially outwardly locatednozzle outlet aperture 309 and a radially inwardly located overflowaperture 305 forming in plate 312 opening means respectivelysubstantially axially aligned with the gap 311 and the passage 305. Theamount flowing through is adjusted s0 as to be greater than the nozzleoutlet can cope with. The filtered liquid dams up in the chamber 308 upto the overflow aperture 305' and begins to liow out through the latter.But the damming up in the chamber 308 reduces the differential pressureat the filter gap t0 zero, and no more liquid fiows through the gap.Thus the filter gap 311 is no longer loaded and cannot become clogged.The centrifuge is operated as a decanter until a sufficiently thick cakeof residue has formed in the cavity 301, after which the'supply is cutoff .at 304. The level in the chamber 308 drops, and the -liquid beginsto filter out of the cav-ity 301 into the chamber 308. At this stage, ofcourse, only as -much as the nozzle-or nozzles if several are used-cancope with is filtered. Thus the residue in the cavity 301 is driedthrough the filtration gap and can then be removed by moving the member310 towards the right, as viewed in FIG. l, whereby any solid materialclinging to the inner surface of the member 310 is stripped from thelatter by the annular seal 318 fixed t0 the outer periphery of the plate307. The member 310 in its closed position engages with a knife edge 310an annular sealing ring 319 located in a groove of the additional plate312'.

FIG. 2 shows a centrifuge with a filtration gap mentioned above. Afiltration gap 311 is left open between the outer rotating closure plate312 and the rotating tubular closure member 310, and in many cases isable to replace a filter fabric normally used in centrifuges of thistype. The advantage of such a gap is that it is automatically cleaned bycentifuging each time the centrifuge is opened. It may readily be used,for example, for separating crystals of a certain size.

The filtration gap is also suitable for so-called silting Y separation.Here, before the liquid to be treated is actually separated in thecavity 301, silting is effected, i.e. before filtration a relativelycoarse-grained material used as an aid to filtration is silied in aclean liquid onto the filter surface-in this case onto the filtrationgap.

The material 313 forms a previous filtration layer for the medium to betreated. The liquid filtering through is forced outwardly by centrifugalforce, i.e. onto the inner wall of the rotating tubular member 310, andaccordingly has to pass through the auxiliary filtering layer 313described. The liquid flows along the inner wall of the rotating membertowards the filtration gap 311 and there leaves the centrifuge filtered.As the filtration gap is relatively long, even a very narrow gap of onlya few tenths of a millimetre wide will have a broad enough aperturesection to let through large amounts of liquid.

The apparatus shown in FIGS. 1 and 2 has proved successful, for example,in decanting and subsequently drying residue from industrial andcommunal waste water.

The decanting action, as mentioned above, can be improved by fittingcertain deliecting means in the actual cavity of the centrifuge, butsuch an improvement, i.e. an increase in efiiciency, can also beobtained if steps are taken to calm the fiow of liquid through thecavity-by suitable means, and above all to slow down the inwardlydirected fiow. FIG. l shows how this can be done.

The partition wall 302 fixed in the cavity 301 should if possible bearranged so as to make the inlet chamber 316 small in comparison withoutlet chamber 317. This reduces the speed of flow of the emergingliquid and increases the separation effect.

What is claimed is:

1. A centrifuge for separating solid particulated particles suspended ina liquid from the latter, comprising, in combination, a rotatable shaft;a pair of plates extending transverse to the axis of said shaft andbeing fixed to the latter axially spaced from each other; a tubularmember surrounding said shaft and being axially movable between a closedposition overlapping the outer peripheries of said plates and formingtherewith a substantially closed centrifuging chamber and an openposition opening said chamber in radial direction, one of said plateshaving an outer diameter slightly smaller than the inner diameter ofsaid tubular member so as to form in the closed position of the latterfilter means in form of a narrow annular gap therewith permitting theliquid to pass therethrough while retaining the particulated solidmaterial, whereas the other plate iiuid-tightly engages the innersurface of said tubular member; and passage means communicating withsaid chamber for feeding solid particulated material suspended in aliquid thereinto.

2. A centrifuge as set forth in claim 1, wherein said shaft has a freeend, the other of said pair of plates being fixed to said free end ofthe shaft and said one plate being located laterally of and beyond saidfree end of said shaft, and including a hollow hub substantially coaxialwith the axis of said shaft and connecting said pair lll 4 of plates toeach other, said passage means extending through said hub.

3. A centrifuge as set forth in claim 1, and including a deflector discin said centrifuging chamber extending in radial direction between saidpair of plates axially spaced funher from said one than from said otherplate and dividing a radially inner portion of said chamber into asmaller inlet chamber and a larger outlet chamber, said passage meanscommunicating with said smaller inlet chamber.

4. A centrifuge as set forth in claim 1, and including at least onedecanting passage extending through said one plate radially inwardly ofsaid filter means.

5. A centrifuge as set forth in claim 4, and including an additionalplate axially spaced from said one plate and on the side of the latterfacing away from the other of said pair of plates, Said tubular memberfluid-tightly engaging in said closed position thereof said additionalplate in the region of the outer periphery of the latter to form betweensaid one and said additional plate a pressure-equalizing chamber, saidadditional plate being formed with opening means respectivelysubstantially axially aligned with said filter means and said decantingpassage in said one plate.

6. A centrifuge as set forth in claim 5, and including a deflector discin said centrifuging chamber extending in radial direction spaced fromand between said pair of plates and dividing a radially inner portion ofsaid centrifuging chamber into two flow passages, said passage meanscommunicating with that ow passage which is located between saiddeliector disc and the other of said pair of plates.

7. A centrifuge as set forth in claim 5, wherein said tubular member hasan annular edge face engaging that face of said additional lplate whichfaces the other of said pair of plates, and including annular sealingmeans providing a duid-tight seal between said edge face and said faceof said additional plate when said tubular member is in said closedposition.

8. A centrifuge as set forth in claim 7, wherein said edge face ends ina substantial knife-edge, and wherein said additional plate is providedwith an annular groove substantially coaxial with said knife edge, andsaid annular sealing means being located in said groove.

References Cited UNiTED STATES PATENTS 1,355,559 10/1920 Mauss 233-21,588,526 6/ 1926 Cleveland 233-2 1,648,790 lll/1927 Sturgeon 233-463,075,693 1/1963 Dega 233-2 FOREIGN PATENTS 588,421 11/1933 Germany.130,495 2/ 1929 Switzerland.

HENRY T. KLINKSIEK, Primary Examiner.

